From the tutorial on calculating U for NiO with response ansatz of Cococcioni et al., I understand the following procedure:
1) ionic relaxation NiO unit cell U_in=0, LDAUTYPE = 2
Use CONTCAR
Specify MAGMOM
2) SCF groundstate calculation of unit cell U_in=0, LDAUTYPE = 2
Use CHGCAR
3) for alpha in [-0.20 ... +0.20] (small pertubations):
SCF (ICHARGE=2) calculation U=J=alpha , LDAUTYPE = 3
NSCF (ICHARGE=11) calculation U=J=alpha , LDAUTYPE = 3
4) calculate U_out from derivates of occupation with respect to alpha.
This leaves me with some questions however:
1) If the MAGMOM is unknown, can the default be used?
2) For step 2, is WAVECAR also required?
2) To calculate U, does step 1 through 4 have to be repeated until U is self-consistent? The ionic structure is different when DFT+U is applied. So I imagine step 1 through 4 is repeated until U_in = U_out
3) If step 1 through 4 is repeated, for step 2, do you use the calculated U value?
4) if step 1 through 4 is repeated, for step 3, do you apply pertubations around the calculated U value?
U=J= [-0.20+U ... +0.20+U]
Lastly, I think there are some typos in the wiki concerning the values for the number of d-electrons, every value in the tabel for d of Ni starts with 8, like 8.488, while in the calculations shown the same floats are used but starting with 4 (4.488 instead of 8.488). The difference is the exact same, such that the result of the equation is correct, but it is quite confusing when reading it for the first time where the tabulated 4.488, 4.438, etc. come from.
Kind regards,
Jeffrey